Hey guys, a few weeks ago a friend of mine asked me to show him a crystal radio I made, which is this one right here. I made it many years ago, and since then I've played around with other variations and even a kit. Then I looked around YouTube and saw that there was no video that really went through step-by-step how to make a crystal radio. So I figured I'd make one using as much scrap pieces as I could.
So here's the video. I hope you enjoy it. Here's the complete circuit diagram, but don't worry, you don't have to understand it in order to make this. The parts we'll have to make are this capacitor and these two coils. So let's start with the capacitor.
To make the capacitor we need some aluminum foil and we're going to cut two 6x6 pieces. Here we go. The first piece of foil I simply taped onto a paper towel roll using masking tape.
You can use any kind of tape you want as long as it's not electrically conductive tape. And I left about a half inch at the bottom here, one centimeter. For the other piece of aluminum foil, cut a 7x7 piece of white paper and tape the aluminum foil onto the middle of it.
Okay, there we go. Next, tape that piece and tape it so that it's wrapped around the paper towel roll. Make it so it's snug fit, but so they can slide up and down fairly easily.
You want the aluminum side facing out so that the paper is facing in. That way the paper is between this aluminum piece and the piece that you'd previously taped onto the roll. Also, I'd ask that the paper be 7 inches by 7 inches. That's because I knew that if it's 7 inches, that paper would fit completely around the paper towel roll.
Because you want this aluminum insulated from this aluminum. Next, cut a piece of wire about 1 foot long. And strip about an inch long piece of insulation off one end of it.
Give it a little bit of a 90 degree turn there. And tape it to the top corner of the free moving piece of aluminum foil. Put a few pieces of tape just to make sure it's fairly snug there. It won't move around.
And then cut another piece of wire the same way. And strip it the same way. And tape it to the bottom of the piece of foil that doesn't move. And there we go, there's our completed capacitor.
Now I'll show you how to make the two coils. Okay, for the coil, I'm going to use this toilet paper roll right here. Make sure you clean it off, you know, get all the toilet paper and glue and stuff that's sticking up off it.
For the wire, I've got all kinds of wire here. This is magnet wire. It's a thin wire, about, I don't know, 22, 24, 26 gauge. And it's covered in enamel insulation.
Basically kind of resin or something. It's called magnet wire and reasons called magnet wire is usually used for making electromagnets I bought this from Radio Shack and came in a package of different ones Can also use wire like this with a thicker insulation, but it is going to take up more room When you wind it on the coil and then I've got this big spool right here Which is what I'm actually going to use a bottle long time ago. I'm never going to use it's a completely it's 26 gauge That's a wire I'm going to use To start for the coil, what I suggest, this is a technique that works well for me, take a piece of masking tape or whatever tape you're using and cut it to the complete length of the toilet paper roll.
Stick it on there. Fold it back if you want. And then take another piece just like that and do it again. Okay, for the first winding is the primary and That's the one that the wire that the antenna is going to be attached to that's your input coil I'm going to start it fairly close to the edge and As I've said to hold it in place peel back the tape and Put it in place.
I'm going to leave about oh, I don't know foot or so wire sticking out Okay, so ready to start. I'm going to do 25 turns. Okay, there we go. I've left about a foot right here on the end. And just lift this up.
While I'm doing this I just want to point out the direction that you start the first coil. This coil. It doesn't really matter. As long as both coils you're going to do are wound in the same direction. I've also lifted the tape.
Put it underneath there. Slightly, very close as I can to the other windings. And put the tape back.
And there we go, that's the first one. Now to work on the second coil. Okay, the second coil, the secondary, is 90 turns, 9-0. And you want to start it 1-8th of an inch away from the coil you just did.
That's quite close. And 90. Okay, the next step is to make a good holder for all of this. So I got this literally pieces of scrap wood.
I screwed a piece of scrap wood to here. And then on the back I also screwed some more pieces of scrap wood together. And the whole idea is it goes like this. You take the capacitor.
And just slide it on like that. So for adjusting the capacitance, you can just do that. Maybe I'll put a Tumtac there. Now, for the coil, you're going to need some way of tuning this coil, because this is a tunable crystal radio. For that, I've got this sort of thing.
What is this? Well... This is simply a piece of paint can. I took a piece of paint can and cut it up and cut a piece of metal to this shape. That way I can make a wiper blade.
I simply put a little screw here and screw that to the top of that. So I just basically bent it into a V shape. That way where it wipes against the coil there, it's fairly smooth surface but comes to a point. I'm going to go ahead and cut this out. Okay, so the next step will be to find out where we're going to put this, probably around there, and put some thumbtacks just to hold it in place.
And I've got to sand the top of the coil right here. But when you sand the top of the coil, that makes contact with the blade. When you sand the top of the coil, you want to make sure you don't short out one wire to the next wire. So when you sand it, you really just want to sand the very surface of the wires, but not in between the wires. I just taped the coil down, but there you can see the finished result.
The next step is to start hooking up some wires here. First thing we'll need is a ground wire connection. For that, I use this trick right here.
What I do is I have a North America, we have plugs like this. This prong right here on the plug is a ground connection, and these two are hot and neutral. But I only want to use this one, so I bought a plug, which you can buy at hardware stores, and then I connected up just a single wire to just this ground connection. And I'll plug it into this extension cord. And I've tested this wall socket that the extension cord is plugged into.
It does, in fact, have a good ground connection. So I'll just need to tape that up here somewhere. Some other suggestions for ground connections.
You can connect to your hot water pipes, your water pipes underneath your sink. You get a radiator, you can connect to that. Anything that's connected to ground.
So next I need an antenna. And for that... I've simply taken a long wire and strung it out.
It's about 15 feet long. So I'll tape that in place probably right here. Next I need a diode. This is a 1N34 diode, a germanium diode.
It works quite well. I've tried a few different ones. And notice it has a gray stripe along one end here.
That's important for positioning this thing properly. So I'm just going to tape that into place. I'll tape it with the stripe facing outwards. The last piece we'll need is this earpiece right here.
It's a 2000 ohm earpiece. Very, very sensitive. Some people use speakers from phones as well, so if you dig up an old phone, you might want to try that.
I just realized I forgot to mention a very important step, and that's to bare these wires right here. So the way I usually do that is I simply take an X-Acto knife and just scrape like that, very gently. You don't want to cut the wire. and do that all around.
You just need to take the insulation off, the enamel, just like we did when we sanded the top of it. Other ways of doing this are to use sandpaper and there's also something you can dip it in, I don't know if it's acetone or something, that just dissolves the enamel. Okay, I've done all four ends right here, all four pieces of enameled wire. Okay, now to start putting it together. I'll start over here with the ground.
Basically just follow the diagram. I just twist things on. Twist them fairly tightly with lots of turns.
I like to put the enameled ones on first, the thin wire first, because the other wires then wrap around those tightly. And one more wire, I need to go from the wiper blade to ground as well, so I'll have to make a wire for that. Okay, now to test.
Okay, to adjust it, you adjust the wiper first so you hear something. If you don't hear anything at all, then just keep moving this back and forth. And then once you find something, adjust the volume using the capacitor. I got something.
I'll just put that in the camera microphone so you can hear it too. Anyway, there you have it. A crystal radio made mostly from junk.
The exception of the diode and the earpiece. Well, thanks for watching. Be sure and check out my YouTube channel, Rimstar Org, for more science and tech videos, including more crystal radio related ones.
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